Lint fixes (#99)

* Replace a single-character string literal with a character literal.

* Use is_some() instead of comparing with Some(_).

* Add code-quotes around type names in comments.

* Use !...is_empty() instead of len() != 0.

* Tidy up redundant returns.

* Remove redundant .clone() calls.

* Remove unnecessary explicit lifetime parameters.

* Tidy up unnecessary '&'s.

* Add parens to make operator precedence explicit.

* Use debug_assert_eq instead of debug_assert with ==.

* Replace a &Vec argument with a &[...].

* Replace `a = a op b` with `a op= b`.

* Avoid unnecessary closures.

* Avoid .iter() and .iter_mut() for iterating over containers.

* Remove unneeded qualification.

lib/cretonne/src/regalloc/reload.rs

@@ -233,7 +233,7 @@ impl<'a> Context<'a> {
             // Create a live range for the new reload.
             let affinity = Affinity::Reg(cand.regclass.into());
             self.liveness.create_dead(reg, dfg.value_def(reg), affinity);
-            self.liveness.extend_locally(reg, ebb, inst, &pos.layout);
+            self.liveness.extend_locally(reg, ebb, inst, pos.layout);
         }
 
         // Rewrite arguments.